The present invention generally concerns rotatable shaft assemblies such as gear reducers and pumps. More particularly, the invention relates to these assemblies and their sealing arrangements.
Rotatable shaft assemblies typically include a housing with at least one axial bore that extends through the housing and through which a driven or driving shaft may pass. Generally, a seal extends between the housing and the shaft to prevent passage of exterior contaminants to the housing's interior area and to prevent escape of lubricant. In this regard, a lip seal may attach to the housing and extend radially inward to abut the rotating shaft so that passage of material is prevented from either direction across the seal. Such seals are advantageous in that they may prevent escape of lubricant from the housing interior if the assembly is inadvertently shifted or tilted during shipping. The rotating shaft may, however, wear the lip seal and thereby limit its useful life.
Labyrinth seals typically have a longer life. The one or more seal elements that form the labyrinth stages do not fully contact the shaft, due to a clearance fit and/or to the passage of lubricant between the seal element(s) and the shaft. These seals may, however, permit leakage of lubricant during shipping.